In many applications different data networks are provided for transporting different data, which must be kept separate from each other in order to avoid an unwanted influence of one data network on another data network. For example, in aircraft different data networks are used to transport data belonging to different security domains, such as an aircraft control domain, an airline information service domain and a passenger information and entertainment services domain. The aircraft control domain comprises those functions which are absolutely necessary for the operation of the aircraft and for the communication with air traffic control. By contrast, the airline information service domain includes functions which are less relevant to security and are therefore not absolutely necessary, but which are still advantageous for the operation of the aircraft as such. Finally, the passenger information and entertainment services domain includes entertainment and communication functions addressing the passengers directly. The latter functions have no relevance to the safety and operation of the aircraft as such. It must be ensured that, e.g., the functions of the aircraft control domain are never impaired by network entities of the airline information service domain or the passenger information and entertainment services domain.
Due to the fact that in aircraft and spacecraft it is generally highly desirable to keep the extent and complexity of the cabling at a minimum, both in view of weight, costs and maintenance efforts, approaches exist to nevertheless transmit data belonging to different domains or data networks at least partially over a common data line. For example, DE 10 2011 076 357 B4 describes a network in which two network access devices are connected to a common data line. Each network access device comprises multiple data interfaces to which respective data networks transporting data of different priorities are connected. The network access devices transmit the data of the different data networks over the common data line in fixed time slots, wherein multiple data packets from the different data networks are inserted into each of the fixed time slots based on the priorities associated with them in order to be able to guarantee a minimum data transmission rate at least for the highest priority data. The receiving network access device distributes the data packets to the correct data interface based on the priorities of the data packets.
It is desirable to increase the overall bandwidth available for data transmission as much as possible without increasing the complexity of the network structure.